1. From the University of Washington (F.C., B.W.D., F.M.L., G.L.R.) and Agilent Technologies (D.B.J., D.S., T.D.L., B.C.), Seattle, Wash; Harvard Medical School (C.I.B.), Boston, Mass; Children’s Hospital and Health Center (J.C.P., A.A.Z.), San Diego, Calif; and the University of Iowa (D.L.A.), Iowa City.